Bug 1660278 - Add libtinfo5 requirement to custom-v8 docker. r=jmaher

This patch fixes an issue in the custom-v8 toolchain where there is tooling missing that is needed to build v8 (the libtinfo5 package).

Differential Revision: https://phabricator.services.mozilla.com/D88310

taskcluster/docker/custom-v8/Dockerfile

@@ -13,6 +13,7 @@ RUN apt-get update && \
       curl \
       libbz2-dev \
       libglib2.0-dev \
+      libtinfo5 \
       pkg-config \
       tar \
       unzip \